For example, a lithium battery has been widely put to practical use in the field of information relevant apparatuses and communication apparatuses by reason of having a high electromotive force and a high energy density. On the other hand, the development of an electric automobile and a hybrid automobile has been hastened also in the field of automobiles from the viewpoint of environmental issues and resource problems, and a lithium battery has been studied also as a power source thereof.
Liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the improvement in structure and material for preventing the short circuit are necessary therefor. In contrast, an all solid lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery.
Such an all solid state battery generally has a cathode active material layer, an anode active material layer, and a solid electrolyte layer formed between the cathode active material layer and the anode active material layer. For example, in Patent Literature 1, an all solid state battery having a solid electrolyte layer with a film thickness of 10 μm to 300 μm and a voidage of 30% or less, containing a sulfide solid electrolyte, is disclosed. Also, pressurizing at a pressure of 30 MPa to 1000 MPa (306 kgf/cm2 to 10200 kgf/cm2) is disclosed as a method for making a voidage of the electrolyte layer into 30% or less.